Note: Descriptions are shown in the official language in which they were submitted.
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
RADIATION CURABLE AQUEOUS COMPOSITIONS
FOR LOW EXTRACTABLE FILM PACKAGING
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a Continuation-In-Part of Application Serial No.
09/538,024 filed
March 29, 2000, now pending.
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to radiation curable aqueous compositions and printing
inks for the manufacture of packaging materials. More particularly, this
invention relates
to radiation curable compositions and printing inks for the manufacture of low
odor food
packaging materials which have low levels of extractable components.
Description of Related Art
Energy curable, low viscosity inks and coatings are typically composed of
mixtures of acrylated oligomers and monomers. Typically monomers are used to
control viscosity of ink or coating formulations for flexographic, gravure,
roller and tower
printing and coating applications. However, diluent monomers do not react
completely
during polymerization upon exposure to ultraviolet (UV) or electron beam (EB)
radiation.
Such unreacted monomers remain as residual components in the dried printing
ink or
coating films and are subject to migration by absorption as well as surface
contact. This
migration of residual components leads to a host of problems, particularly for
printing or
coating "odor" and "off-taste" sensitive packaging for packages such as
containers for
food, beverages, tobacco, perfume, etc., and for such applications which
require
negligible amounts of extractables from cured printing inks or coatings such
as
pharmaceutical and health care packaging. In addition, sometimes solvents are
employed to achieve a coating of lower viscosity.
An example of a solvent based coating is described in U.S. Patent 5,824,717,
Merill et al., which discloses peroxide and radiation (energy) curable
compositions
containing isobutylene copolymers having acrylate functionality, and
optionally a filler.
The disclosed copolymers are acrylate modified copolymers of an iso-olefin of
4 to 7
carbon atoms and para-alkylstyrene co-monomers. Merrill discloses that the
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
percentage of extractables from the cured composition is negligible, and that
the cured
composition is suitable for use in the manufacture of a variety of high purity
rubber
goods used in the pharmaceutical and health care industries. Merrill further
discloses
that the compositions may be used as condenser packings, food contact
material, wire
cable insulation materials, and in the manufacture of high purity hoses.
Merrill discloses
that coatings are prepared by dissolving the copolymer in toluene as the
primary
solvent.
Problems resulting from odor, off-taste and residual extractables with
currently
available UV/EB printing inks and coatings has kept energy curable products at
bay
from the high volume packaging market, which still is largely served by
conventional
solvent or water based flexo printing inks and coatings which require the
removal of the
solvent or water before curing. Acrylated oligomers typically have
viscosities, which are
too high to be used per se (i.e., without a monomer diluent) for making low
viscosity
coatings and printing especially inks.
The use of water as a diluent for mixtures of UV/EB curable acrylated
oligomers
is disclosed, however, in U.S. Patent 6,011,078 for application in wood and
floor
coatings. The formulations are dispersions or emulsions, which require prior
evaporation or imbition of water on non-absorbent substrates before exposure
to light.
There continues to be a need for a monomer and solvent free, UV/EB curable
homogeneous aqueous printing ink and coating formulations, which produce cured
films
having insignificant odor, off-taste, and/or extractable components.
SUMMARY OF THE INVENTION
The invention is an improved radiation curable, homogeneous aqueous
composition comprising: a water soluble compound which contains at least one
a(3
ethylenically unsaturated, radiation polymerizable group and water, wherein
the
improvement comprises that when a surface is coated with the composition and
exposed to an effective amount of actinic radiation in the presence of water,
a cured film
is formed wherein less than 50 ppb of uncured residue is extractable therefrom
when
immersed and heated in 10 ml of a simulant liquid per square inch of cured
film.
A further embodiment of this invention is a method for packaging a commercial
food item or pharmaceutical comprising the steps of providing an actinic
radiation
curable homogeneous aqueous composition comprising a water soluble compound
which contains at least one a,a-ethenically unsaturated, actinic radiation
polymerizable
2
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
group and water, applying said homogeneous aqueous composition onto a surface
of a
packaging material, efficiently irradiating the surface with actinic radiation
in the
presence of water, thereby producing a film, and packaging said commercial
food item
or phamaceutical with said packaging material such that said food item or
pharmaceutical is in direct contact with said film.
Another embodiment of this invention is a commercial food item in a packaging
material having a surface in direct contact with said commercial food item,
said surface
being coated with a film produced by the method comprising providing an
actinic
radiation curable, homogeneous aqueous composition, comprising a water soluble
compound which contains at least one a,~3-ethylenically unsaturated, actinic
radiation
polymerizable group and water, applying said homogeneous aqueous composition
onto
a surface of said packaging film, and efficiently irradiating the surface with
actinic
radiation in the presence of water.
Another embodiment of this invention is a packaging material comprising a
substrate and a cured film adhered to the substrate surface derived by
providing a
homogeneous aqueous composition consisting essentially of a water soluble
oligomer
containing two or more acrylic groups, and water, wherein the homogeneous
aqueous
composition is applied to the substrate and cured by actinic radiation in the
presence of
water, such that less than 50 ppb of oligomer residue is extractable from the
cured film
when immersed and heated in 10m1 of a simulant liquid per square inch of cured
film.
Another embodiment of this invention is an improved method of packaging a
commercial food item or pharmaceutical with a film meeting government
requirements
for commercial food or pharmaceutical packaging; wherein the improvement which
comprises utilizing as said film, an actinic radiation cured homogeneous
aqueous
homogeneous composition having a water soluble compound containing at least
one
a,~i-ethylenically unsaturated radiation polymerizable double bond group and
water.
A still further embodiment of this invention is a method for producing a low-
extractable FDA complaint cured film comprising the steps of providing an
actinic
radiation curable homogeneous aqueous composition comprising a water soluble
compound which contains at least one a,~3-ethenically unsaturated, actinic
radiation
polymerizable group and water, applying said homogeneous aqueous composition
onto
a surface, efficiently irradiating the surface with actinic radiation in the
presence of
water, thereby producing a cured film such that less than 50 ppb of oligomer
residue is
extractable from the cured film when immersed and heated in 10m1 of a simulant
liquid
3
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
per square inch of cured film.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a novel homogeneous aqueous radiation curable
composition which comprises a water soluble compound which contains at least
one
a,~3-ethylenically unsaturated, radiation polymerizable group; and water.
Preferably, the
water soluble compound is a water soluble oligomer containing two or more
acrylic
groups; and the composition may also contain a photoinitiating system. As used
herein
the term "low-extractable film" is intended to mean a cured film composition
substantially free of solvent extractable oligomer (i.e., less than 50 ppb) or
residual
components when subjected to solvent under a solvent extraction tests
hereinafter
described. The curable composition of this invention may also contain a
colorant such
as a dye or pigment. Such a colored composition may be used as a printing ink
in
printing operations or simply to form a colored coating. As used herein, the
term
"printing ink" has its conventional meaning, i.e., a colored liquid composed
of a colorant,
typically a solid pigment, dispersed in liquid vehicle. In particular the
radiation curable
printing ink of this invention comprises a pigment and a liquid vehicle.
Although the
homogeneous aqueous curable composition may be used in a number of
applications
which require limited extractables, the composition is particularly useful in
the packaging
industry, and more specifically in the food packaging industry wherein cured
coatings
and/or printed matter come in contact with food products at ambient and/or
processing
conditions. Cured compositions of this invention impart substantially no
contamination to
products contacted by the cured compositions such as foods, drinks, cosmetics,
pharmaceuticals, as well as materials used for medical and health care and
procedures.
In particular, cured compositions of this invention have insignificant or no
odor, and
impart substantially no off-taste to food products contacted by the cured
compositions.
Homogeneous Aqueous Curable Composition
The homogeneous aqueous radiation curable composition of this invention
contains as the essential ingredients, a water soluble compound which contains
at least
one a, ~3-ethylenically unsaturated, radiation polymerizable group, preferably
a water
soluble oligomer containing two or more acrylic groups; water; and optionally
a
photoinitiating system activatable by actinic radiation such as UV radiation;
and/or a
colorant such as a dye or pigment.
4
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Water Soluble Compound
As used herein the term "water soluble compound" means a radiation curable
compound which contains a limited number of water solubilizing groups, such as
carboxyl, hydroxyl, ether and the like, sufficient to provide solutions of the
compound in
water at ambient temperatures; and in addition which contains at least one a,
~i-
ethylenically unsaturated, radiation polymerizable group. Preferably the water
soluble
compound is an oligomer. As used herein the term "oligomer" is intended to
include
compounds which contain two or more terminal, or pendent, a, (3-ethylenically
unsaturated groups which are linked through a polymeric backbone, or through
similar
linking groups to a central aliphatic or aromatic backbone. The water soluble
compounds used in this invention may be an epoxy acrylate, an epoxy
methacrylate, a
polyether acrylate, a polyether methacrylate, a polyester acrylate, a
polyester
methacrylate, a polyurethane acrylate, a polyurethane methacrylate, a melamine
acrylate, or a melamine methacrylate. Typically the acrylate is an aromatic or
aliphatic
acrylate or methacrylate and preferably the compound is a diacrylate ester of
an
alkanolglycidyl ether such as 1, 4-butanedioldiglycidyl ether, an ethoxylated
aromatic
epoxide and ethoxylated trimethylolpropanetriacrylate, ethoxylated
trimethylolpropanetrimethacrylate, ethoxylated aliphatic or aromatic epoxy
acrylate,
ethoxylated aliphatic or aromatic epoxy methacrylate, polyoxyethylene glycol
diacrylate;
polyoxyethyleneglycol di- methacrylate. Preferably, the ethoxylated aromatic
epoxide
contains 6 to 20 ethoxy groups.
Suitable water soluble compounds are aliphatic and aromatic epoxy acrylates
and epoxy methacrylates, aliphatic compounds preferably being employed. These
include, for example, the reaction products of acrylic acid or methacrylic
acid with
aliphatic glycidyl ethers.
Further suitable compounds are polyether acrylates and methacrylates,
polyester
acrylates and methacrylates and polyurethane acrylates and methacrylates.
Among
these, preference is given to the reaction products of acrylic or methacrylic
acid with the
polyesterols and polyetherols which were described as polycondensates.
Particular
preference is given to the radiation curable acrylates described in EP-A-126
341 and
EP-A-279 303. Polyetherols employed in this context are preferably
alkoxylated,
especially ethoxylated and/or propoxylated, mono-, di-, tri- or polyfunctional
alcohols.
Other suitable compounds are melamine acrylates and methacrylates. These are
5
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
obtained, for example, by esterifying the free methylol groups of the resins
with acrylic
acid or methacrylic acid, or by transetherification of etherified melamine
compounds
with hydroxyalkyl methacrylates, for example hydroxyethyl, hydroxypropyl and
hydroxybutyl methacrylate, hydroxybutyl acrylate.
Still further suitable compounds are, in general, thickeners which contain
unsaturated groups. These include on the one hand polyurethane thickeners,
which
contain a,~-ethylenically unsaturated double bonds as a result of the
incorporation of
the above mentioned hydroxyalkyl methacrylates, hydroxyalkyl acrylates. They
also
include polyacrylate thickeners, which are obtained by polymer-analogous
reaction of,
for example, hydroxyl-containing polymers, or polymers containing acid groups,
with
epoxide-containing methacrylates, acrylates for example glycidyl methacrylate,
glycidyl
acrylate, or of hydroxyl-containing polymers by esterification with
methacrylic acid,
acrylic acid or reaction with methacrylic anhydride, acrylic anhydride or by
reaction with
NCO-terminated methacrylates, methacrylates for example methacryloyl
isocyanate,
isocyanatoethyl methacrylate, isocyanatoethyl acrylate etc. They additionally
include
polyvinyl alcohols, which are modified, for example, by reaction with
methacrylic
anhydride, acrylic anhydride or by esterification with methacrylic acid,
acrylic acid with
groups containing double bonds. Finally, they include copolymers comprising
malefic
anhydride as comonomer, the polymer being modified by ring opening of the
anhydride
with the above mentioned hydroxyalkyl methacrylates, hydroxyalkyl acrylates or
with
hydroxy vinyl ethers, for example butanediol monovinyl ether,
cyclohexanedimethanol
monovinyl ether etc., with double bonds.
Particularly preferred water soluble compounds include diacrylate esters of an
alkanolglycidyl ether; wherein the alkanol has 2 or 3 hydroxy groups, such as
a
diacrylate of 1,4-butanedioldiglycidyl ether; a triacrylate of
trimethylolpropane-diglycidyl
ether, or a mixture thereof; and ethoxylated acrylic oligomers, such as an
ethoxylated
trimethylolpropanetriacrylate; an ethoxylated trimethylolpropane diacrylate;
or a mixture
thereof; wherein the ethoxylated oligomer contains 9-12 ethoxy groups. A
particularly
preferred water soluble compound is the diacrylate ester of 1,4-
butanedioldiglycidyl
ether, which is available from BASF Corporation, Charlotte NC, as Laromer LR
8765
aliphatic epoxy acrylate.
The homogeneous aqueous, radiation curable coating compositions of this
invention contains from about 0.1 to about 95% by weight of the water soluble
radiation
curable compound, preferably from 75 to 95 wt. %, of the water soluble
radiation
6
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
curable compound made of at least one a,~i-ethylenically unsaturated,
radiation curable
double bond. Preferably, the homogeneous aqueous curable composition contains
between about 5 wt. % and about 50 wt. % water. Typically the water soluble
compound is added to the coating composition in an amount sufficient to attain
a solids
content ranging from 75 to 95 wt. %.
Photoinitiating System
Unless the homogeneous aqueous radiation curable composition is formulated
specifically for use with electron beam curing, the homogeneous aqueous
radiation
curable coatings of this invention optionally may contain an addition
polymerization
photoinitiator which generates free radicals upon irradiation with UV at a
wavelength
ranging from 200 to 420 nanometers. Thus, the homogeneous aqueous radiation
curable coating compositions of this invention optionally contains from 0 to
about 10 wt.
of a photoinitiating system. Such a photoinitiating system has one or more
compounds
that directly furnish free radicals when activated by UV radiation. The
photoinitiator
system may also contain a sensitizer that extends spectral response into the
near
ultraviolet, visible and near infrared spectral regions. When cured by UV
radiation, the
coating compositions typically have from about 0.05 to about 20 wt. %,
preferably from
0.05 to 10 wt.% and, in particular, from 0.1 to 5 wt.% of a photoinitiating
system. A wide
variety of photoinitiating systems may be used provided that the components of
the
system or their residue after polymerization, are non-migratory or
substantially
teachable from the cured film. Useful photoinitiators of this type are
described by B.M.
Monroe and G.C. Weed in an article entitled "Photoinitiators for Free-Radical-
Initiated
Photoimaging Systems'; Chem. Rev. 1993, 93, 435-448. Photoinitiators which may
be
used alone or in combination, include benzophenone, alkylbenzophenones, such
as 4
methylbenzophenone, halomethylated benzophenones, Michler's ketone (4,4'
bisdimethylamino-benzophenone), halogenated benzophenones, such as 4-
chlorobenzophenone, 4,4'-dichloro-benzophenone, anthraquinone, anthrone (9,10-
dihydro-9-anthracenone), benzoin, isobutyl benzoin ether, benzil and benzil
derivatives,
such as benzil dimethyl ketal, and phosphine oxides or phosphine sulfides,
such as
bisacylphosphine oxides, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, etc.
Preferred photoinitiators which may be used alone or in combination with
others are 4-
(2-hydroxyethoxy)-phenyl-(2-hydroxy-2-methylpropyl)-ketone; isopropyl-
thioxanthone;
and the like.
7
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
If desired the photoinitiating system may additionally comprise a synergist,
preferably a tertiary amine. Examples of suitable synergists are
triethylamine,
dimethylethanolamine, methyldiethanolamine, triethanolamine, amino acrylates,
for
example amine-modified polyether acrylates, such as the BASF Laromer°
grades LR
8956, LR 8889, LR 8869, LR 8894, PO 83F and PO 84F, and mixtures thereof. In
the
case of pure tertiary amines they are generally employed in an amount of up to
5 wt. %,
in the case of amino acrylates in an equivalent amount corresponding to the
number of
amino groups present, based on the overall amount of the coating compositions.
Colorant
The homogeneous aqueous radiation curable composition of this invention may
additionally contain from 0 to about 50 wt. % of a colorant such as a dye or
pigment. ,
Preferably, such dyes or pigments, while soluble or dispersible in the curable
composition, form permanent non-migratory components in the coated cured
composition. When used as a radiation curable ink, the homogeneous aqueous
coating
solution typically contains one or more solid pigments dispersed therein. The
pigment
may be any conventional organic or inorganic pigment such as zinc sulfide,
Pigment
White 6, Pigment Yellow 1, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow
13,
Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 63, Pigment Yellow 65,
Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83,
Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 106, Pigment Yellow 114,
Pigment Yellow 121, Pigment Yellow 126, Pigment Yellow 127, Pigment Yellow
136,
Pigment Yellow 174, Pigment Yellow 176, Pigment Yellow 188, Pigment Orange 5,
Pigment Orange 13, Pigment Orange 16, Pigment Orange 34, Pigment Red 2,
Pigment
Red 9, Pigment Red 14, Pigment Red 17, Pigment Red 22, Pigment Red 23, Pigment
Red 37, Pigment Red 38, Pigment Red 41, Pigment Red 42, Pigment Red 57,
Pigment
Red 112, Pigment Red 122, Pigment Red 170, Pigment Red 210, Pigment Red 238,
Pigment Blue 15, Pigment Blue 15:1, Pigment Blue 15:2, Pigment Blue 15:3,
Pigment
Blue 15:4, Pigment Green 7, Pigment Green 36, Pigment Violet 19, Pigment
Violet 23,
Pigment Black 7 and the like. The colorant may also be selected from a dye or
pigment
certified for use by the Federal Food Drug and Cosmetics Act and include FD&C
Red
No. 3, D&C Red No. 6, D&C Red No. 7, D&C Red No. 9, D&C Red No. 19, D&C Red
No. 21, D&C Red No. 22, D&C Red No. 27, D&C Red No. 28, D&C Red No. 30, D&C
Red No. 33, D&C Red No. 34, D&C Red No. 36, FD&C Red No. 40, D&C Orange No. 5,
8
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
FD&C Yellow No. 5, D&C Yellow No. 6, D&C Yellow No. 10, FD & C Blue No. 1,
Iron
Oxide Yellow, Iron Oxide Brown, Iron Oxide Red, Iron Oxide Black, Ferric
Ammonium
Ferrocyanide, Maganese Violet, Ultramarine Blue, Chrome Oxide Green, Hydrated
Chrome Oxide Green, Titanium Dioxide. Pigment compositions which are also
useful
in the energy curable inks of this invention are described in U.S. Patents
4,946,508;
4,946,509; 5,024,894; and 5,062,894 each of which is incorporated herein by
reference.
Such pigment compositions are a blend of the pigment along with a
poly(alkylene oxide)
grafted pigment. Homogeneous aqueous curable compositions containing a
colorant
are particularly useful in formulating radiation curable printing inks for use
in
conventional printing such as flexographic, gravure letterpress dry-offset and
lithographic printing. Although each of these printing operations require
printing inks
with specific characteristics such as specific viscosity ranges, such
characteristics can
be realized by adjusting the ratio of solids including the pigment and
oligomer, and
water.
Other Adjuvants
The homogeneous aqueous curable compositions may contain additional
adjuvants provided that the additional adjuvants do not materially affect the
essential
nature of the composition and that the adjuvants or their residue after
polymerization,
are non-migratory and are substantially not teachable from the cured film.
Thus the
homogeneous aqueous radiation curable compositions and inks of this invention
may
contain the typical adjuvants to adjust flow, surface tension and gloss of the
cured
coating or printed ink. Such adjuvants contained in inks or coatings typically
are a
surface active agent, a wax, fillers, matting agents, or a combination
thereof. These
adjuvants may function as leveling agents, wetting agents, dispersants,
defrothers or
deareators, or additional adjuvants may be added to provide a specific
function.
Preferred adjuvants include fluorocarbon surfactants such as FC-430,a product
of the
3M company; silicones, such as DC57, a product of Dow Chemical Corporation;
polyethylene wax; polyamide wax; paraffin wax; polytetrafluoro-ethylene wax;
and the
like.
The homogeneous aqueous curable coating compositions may contain from
about 0 to about 50 wt. %, preferably from about 1 to 50 wt. % of a filler.
Examples of
suitable fillers are silicates obtainable by hydrolyzing silicon tetrachloride
(Aerosil° from
Degussa), siliceous earth, talc, aluminum silicates, sodium aluminum silicates
9
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
magnesium silicates, etc. The coating compositions may also include from 0 to
20 wt.
of protective colloids and/or emulsifiers. Suitable emulsifiers are those
commonly
employed as dispersants in the context of aqueous emulsion polymerization and
known
to the skilled worker, such as those described in Houben-Weyl, Methoden der
Organischen Chemie, Volume XIV/1, Makromoleculare Stoffe, Georg-Thieme-verlag,
Stuttgart, 1961, pp. 411-420. Suitable protective materials include
polyvinylalcohol,
polyvinypyrrolidone, cellulose, cellulose derivatives, starch, starch
derivatives, gelatin,
gelatin derivatives, etc.
Preparation of Low-Extractable Cured Film
An embodiment of this invention is a method of forming a low-extractable film.
In
this method, the homogeneous aqueous composition previously described is
applied
onto a surface of a substrate and without any substantial removal of water,
the applied
homogeneous aqueous composition is irradiated with high energy electrons or UV
radiation in the presence of the water to form a cured film. The homogeneous
aqueous
composition may be applied to the substrate surface as a uniform coating using
any
conventional coating technique. Thus the composition may be spin coated, bar
coated,
roller coated, curtain coated or may be applied by brushing, spraying, etc.
Alternatively
the homogeneous aqueous composition may be applied imagewise to the substrate
surface, for instance as a printing ink, using any conventional printing
technique. Once
the homogeneous aqueous coating composition is applied to the substrate
surface, it is
immediately cured in a single step without any prior removal of the water,
using either
high energy electrons or UV radiation. Typically the high energy electrons
have an
energy between 50 and 200 kV electrons and preferably between 85 and 180 kV
electrons and are typically produced by high energy electron device. The
dosage of
high energy electron ranges from about 2 to about 4 megarads (Mrads); and
preferably
from 2.7 to 3.5 Mrads. UV irradiation may be carried out using any
conventional off-
contact exposure device which emits within the spectral region from about 200
to about
420 nanometers. The water in the coated composition, even on non-absorbent
surfaces, does not interfere with curing process, but rather promotes complete
curing of
the oligomer into a completely cured film or image with little or no
extractable oligomer.
Water is believed to be removed concurrently with the curing process and/or
subsequently during manipulation of the substrate. As used herein the term
"cured film"
is intended to include a continuous cured film composition as well as a
discontinuous
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
cured ink image composition. In either sense of the term, the cured film is
adhered to a
substrate and has an outer "cured surface" which defines the surface area used
in the
extraction protocols fully described hereinbelow.
Substrate
The substrate and its surface may be composed of any typical substrate
material
such as plastics, for example polystyrene, polyvinylchloride, polynaphthelene
terephthalate, polyacrylate, polyacrylic, metals, composites, glass, paper,
etc.; and the
cured coating on the substrate may be used in a variety of applications where
low or no
contamination from the substrate is required. Preferably, the substrate is a
food
packaging material formed of a sheet material, a container such as a bottle or
can, or
the like. More preferably, the food packaging material is selected from a
polyolefin,
metalized polyethylene terephthalate, polystrene, polycarbonate, polyurethane,
polyesters, polyamide, polyimide or a metal; more preferably a polyethylene, a
polypropylene, an aluminum foil or a metal container. Alternatively, the
packaging
material may be used to contain cosmetics, biological materials such as
proteins or
specimens, pharmacuticles etc.
Extractable Components
The majority of applications where health safety questions arise relates to
plastics films in direct contact applications with food, cosmetics toiletries,
medicines,
drugs and children's toys. However, the majority of applications are in
packaging and,
for brevity, we shall use the term "packaging" to comprise all contact
situations. Food
packaging is by far the biggest application for plastic film packaging. The
consumer is
anxious about and the plastics merchant responsible for health safety of the
packaged
food. Many other aspects of food quality are also affected by packaging.
Therefore, it
is essential to evaluate the sum total of interactive effects to assess the
acceptance of
the food by the consumer. Processed foods are often formulated (e.g. with
additives) or
processed (e.g. dehydrated) as to enhance storage life and reduce decay. On
the other
hand, this mixture of different foods, or combination, can lead to further
reactions.
Thus, foods almost invariably change with time usually for the worse. Thus, it
is
necessary to evaluate the health risk associated with the packaging of foods
which
have been in contact with plastics films.
To evaluate the scientific basis of health safety, it is necessary to set up a
11
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
standardized model system which reduces any food packaging situation (or
indeed any
food contact situation) to its elements. A typical element can be considered
as a barrier
between food and its environment or any hazard arising from interactions
between
components. In reality, of course, packages are not uniform, and more than one
element type may be involved. Also, there may be scale effects to consider. To
better
understand the sum effect of the component interactions models are used to
integrate
up to the whole package.
Components for interaction include: food; plastic film; residual components;
additives; volatile components; non-volatile components and environment.
Plastics film
is defined as the high molecular weight polymer. Additives are the non-
polymeric
components added subsequently to the manufacture of the original polymer and
include
processing agents such as heat stabilizers and end use improvers such as UV
stabilizers, anti-static agents, etc. Residual components are those traces of
raw
materials from the plastic film which did not react to form polymer in the
original
manufacturing process, and were not removed by subsequent purification. These
include unreacted monomers (e.g. styrene in polystereyne for example,
carpolactam in
nylon for example, and VCM in polyvinyl chloride for example), but traces of
solvents
and unchanged catalysts would also be included. For thermosetting polymers
(e.g.
polyurethane), however, residual components the basic formulation from which
the
thermoset has been made would be included. Decomposition products arising at
any
stage (e.g. acetaldehyde from PEP) can be classified as volatile components,
or
residual reactants. Environment includes all odorous and non-odorous
components
which can diffuse into or through the plastic itself. The most important
materials
concerned war oxygen, water vapor and carbon dioxide; although in certain
situations
other materials may be significant (e.g. chlorine form sterilization). Odorous
components are those which are capable of changing the taste or smell
properties of
the food or plastic. Some interactions have purely technological significance
and are of
no importance. However, some are relevant to health and safety and are listed
below:
12
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Interactions Relevant to Health and Safety
Component From To
Non-volatile food plastics film
Volatile food environment
polymer plastics film Food
Volatile plastics film Food
additives plastics film Food
Radiation
Radiation is sometimes applied deliberately to food, film or a filled package
for
sterilization. Its use for this purpose is largely confined to storage and the
packaging of
pharmaceutical products. In using radiation, care must be exercised on two
counts.
First, legislative constraints apply to the limits of radiation that may be
used in
connection with given foods. Second, intense radiation may lead to degradation
of
many plastics, especially polyolefins (by chain, scission, crosslinking,
oxidation, etc.)
and give rise to odor. Advantageous radiation is largely UV (and a certain
amount of
infra-red) from daylight or fluorescent lamps where the effects on food may be
significant; for example, exposure of milk to sunlight for three hours reduces
the Vitamin
C content and largely destroys the riboflavin content. These effects, and
similar ones on
other foods, relate to nutrition as opposed to toxicity, and hence the effects
on healthy
are seldom serious and never acute. In fact, UV radiation has been found to be
beneficial due to its sterilizing effects on pathogens.
A transparent film is often required for visibility of the food at point of
sale.
Where the greatest barrier to radiation is required, this is best achieved not
by selecting
a particular plastic, but by pigmentation of the plastic. Over 90 percent of
all radiation
transmission is eliminated by the pigment used to achieve normal coloring of
the plastic.
Some reduction in UV transmission can also be achieved by incorporating UV
absorbers. Some pigments have recently been developed, which are transparent
to
visible light, but relatively opaque to UV. These may overcome the problem of
reducing
UV transmission while retaining the desired transparency mentioned above. Of
course,
radiation exposure can also be reduced or eliminated by thick coatings,
printing inks, or
using opaque components in laminates, e.g. paper.
13
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Migration
Migration is mass transfer (transport) between plastics and food. It can
operate
in two ways, from plastic to food (which is the normal meaning) or from food
to plastic
(termed as "negative migration"). It can have effect on the nutritional
quality of food if
certain components of the food are lost to a significant extent. The main
influence is
loss of preservative, but some cases have occurred leading to nutritional
quality of food
if certain components of the food are lost to a significant extent. The main
influence is
loss of preservative, but some cases have occurred leading to nutritional or
organoleptic
changes, e.g. extraction of fat component of milk into polyolefins. If a
colorant, for
example, is extracted from food, the effect on the food is usually not
significant, but the
consequential discoloration of the film (staining) is likely to be
unattractive.
There is no documented case of any proven health hazard arising from migration
to food from plastics film (or indeed any plastic). Most legislation or
regulations cover
migration and organolepsis. There are three basic types of migration
mechanisms:
non-migrating; spontaneously migrating; and leaching.
Non-migrating migration includes high molecular weight polymer components
contacting most foods and some inorganic residues and a few inert (relative to
plastics)
foods, e.g. dry sugar and salt. Spontaneous migration occurs in the absence of
food
contact, i.e. the migrant diffuses out, into the environment and the food.
Leaching
occurs if the plastic is in contact with food or other food simulant
(extractant). It is
obvious that there must be some physical or chemical action which changes the
transport mechanism of the migrant and this can be in two ways: (1 ) where the
migrant
has a relatively high diffusion coefficient in the plastic, but is not
volatile, wherein as
soon as contact is established, the surface layer of migrant is dissolved, and
the
concentration of extractant in the food increases; and (2) where the food or
one of its
components, penetrates the plastic to a certain depth and the plastic matrix
is
substantially changed to the point where mobility of the component within it
is increased
greatly to the point where the component diffuses out through this layer into
the food.
The second mechanism is the more difficult of the two to measure in terms of
scientific
analysis and has only recently become understood. However, it is also the most
important, as it is a concern for most additives in plastics contacting most
foods.
As mentioned, the "simulant liquid" should ideally be the food to be packaged,
and sometimes it can be used. However, severe problems usually arise, namely
decomposition of the food making any analysis difficult, non-homogeneous
distribution
14
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
of migrant, and the need to ensure that the film is suitable for a wide range
of foods.
Therefore, "food simulants" are used instead which are liquids which are
convenient for
analysis and mimic the action of food. A range of simulants has also been
developed,
based on two-component mixtures, which may be more realistic. Components of
these
include tetrahydrofuran, methanol, water and choloform. Commonly used food
simulants include:
Food Type Most Usual SimulantLess Usual Simulant
aqueous distilled water mains water
acidic 3% aqueous acetic 2% aqueous acetic
acid acid;
citric acid aqueous
solution; lactic
acid
aqueous solution
and
N/10 hydrochloric
acid
alkaline distilled water aqueous sodium
carbonate
alcoholic low 15% aqueous ethanol10% aqueous ethanol
alcoholic high 50% aqueous ethanol
fatty olive oil n-hexane
HB 307 n-heptane
50% aqueous ethanol
other vegetable
oils, e.g.
arachis, sunflower
see,
groundnut, teaseed,
cocoa fat
Migration tests are typically carried out at normal processing temperatures,
the
following being typical: sterilization @ 115°C; boil-in-the bag @
100°C; tropical storage
@ 38°C; and normal refrigeration @ 4 or 5°C. Frequently,
40°C is used in what is
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
assumed to be an accelerated test equivalent to migration at 23° C for
a longer period.
There has been much legislation on the overall or global limit on migration;
which
may be defined in terms of concentration in food, where 50 to 60 ppm is
typical, or
migration per unit area. The arguments for the justification of limits are:
protection from
toxic hazard; protection from adulteration; and a reduction in analytical
testing
requirements since it would not be necessary to test an extract for health
hazard which
migrates at a level below the global migration limit.
The methodology oriented to food packaging, would apply with some changes,
mostly of emphasis, to the packaging of drugs, medicines, cosmetics and
toiletries. The
major difference being that toxicity testing is on contact with skin or other
body surface,
or inhalation in the case of aerosols. Devising a system for regulating
plastics films in
contact with food, designed to safeguard pubic health, is a complex scientific
problem.
Both packaging and the use of plastics films have had an explosive growth in
the last
few decades, and hence relevant regulatory systems have experienced some
difficulty
keeping up with progress and are continually under review and change. In the
United
States, for example, packaging materials are within the scope of the Food and
Drugs
Administration (FDA) of the Department of Health, Education and Welfare. The
FDA
regulations include an enormous list giving specifications of base polymers
and
additives. Usage of plastics and their components is permitted in terms of
type of food
stuff, temperature, application type (e.g. film, molding, or polymeric
composition). In
many instances, the United States regulations are accepted by foreign
countries having
no detailed statue or legislation and compliance with them is often required.
Organolepsis
In choosing a food item, a consumer usually decides in principle on a type,
e.g.
meat or poultry for protein; potatoes, rice or bread for carbohydrate;
vegetables; fruit;
etc. When choosing which actual product to purchase within the type at the
point of
sale, however, stated nutritive value or content may have an influence. Yet,
the major
factors are related to perception through the five major physical senses of
sight,
hearing, touch, taste and smell. These are called organoleptic effects, and
the totality is
orgnaolepsis. In packaging they are confined mainly to the sense of smell and
taste.
Plastics films contacting food, for example, are not usually required to
contribute
to the taste or smell of the food. On the contrary, it is usually required
that they should
not do so. If the taste or smell properties of the food are changed in any
way, the result
16
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
is almost invariably considered unfavorable. If the change is sufficiently
unpleasant the
result is called "off odor", "off flavor" or "tainting". These have a similar
mechanistic
rationale to toxic hazard, in that they arise from interactions between the
food and
plastic or the environment. With rare exceptions, most high molecular weight
polymers
are tasteless and odorless; thus the majority component of all commercial
plastics films
will not give rise to an off flavor or off odor of any food. This is a
remarkable
generalization that can not be made for all packaging materials. Volatiles
liable to
diffuse from the plastic to the food are divided into those residual from the
manufacturing process (hence also including residual reactants); degradation
products
formed during the conversion process; and additives. As for degradation
products
formed during the conversion process, these typically arise from
polymerization. Some
plastics decompose slightly on heating. In a few cases, such as polystyrene
and nylon,
the main reaction is depolymerization and the by product is monomer or
oligomer. In
the majority of cases the products are not those which would be obvious.
No mechanical equipment yet exists which can be reliably used for odor or
taste
testing. Also, although animals can occasionally be used for special cases,
they are not
suitable for testing of plastics. Consequently, human groups must be used and
the
human panel members must give an indication of the nature of the off odor or
off taste.
Although not prima facie essential, it is desirable in selecting individuals
for a panel that
their sensory reactions are checked against an identifiied specific stimuli.
Low Extractable Films
Homogeneous aqueous radiation curable compositions of this invention have the
unique characteristic in that a coating of the composition on a surface, when
cured with
high energy electrons or UV radiation in the presence of the water, forms a
cured film
from which less than 50 ppb of the water soluble oligomer or residual
components are
extracted by a simulant liquid under an extraction test such as that described
hereinbelow. As used herein the term "simulant liquid" is intended to mean a
liquid or
solvent which closely simulates a substance which is expected to contact the
cured film
under conditions its intended use. Thus, for example when the cured film is
incorporated into a food packaging material, the simulant liquid should
simulate the
packaged food during both processing and storage. In this instance the
simulant liquid
is preferably a "food simulant".
Extraction procedures employing food simulants are described in a publication
17
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
entitled "Guidance for Industry Preparation of Premarket Notifications for
Food Contact
Substances: Chemistry Recommendations'; September 1999, available from the
Office
of Premarket Approval (OPA), HFS-215, Center for Food Safety & Applied
Nutrition
(CFSAN), FDA, 200 C. St., S.W., Washington, DC 20204. According to FDA
procedure,
a sample of the cured film is immersed in food simulant (i.e. a solvent or
solvent
mixture) simulating the food type which would contact the cured film during
normal
processing, storage and use.
The amount of food simulant used in the extraction is determined from the
exposed surface area of the cured film. Thus, for each square inch (6.45
square
centimeters) of cured film, 10 ml of food simulant is used in the extraction.
Examples of
food simulants suitable for use in the present invention include a 10%
ethanol/water
solution; a 50% ethanol/water solution; a 95% ethanol/water solution; a food
oil; a
fractionated coconut oil having a boiling range of 240-270°C and
composed of saturated
C$ (50-65%) and Coo (30-45%) triglycerides; a mixture of synthetic Coo, C~2,
and C~a
triglycerides; and the like. In one extraction test, the immersed sample is
heated to at
least 40°C for 240 hours. In a more rigorous extraction test, the
immersed sample is
initially heated to about 121 °C for 2 hours then heated to about
40°C for 238 hours.
When the cured film forms on the inner surface of a container such as a can or
beverage bottle, an appropriate amount of food simulant may be added to the
container
and tested. Typically the cured film is tested using a migration cell in which
a specimen
of known surface area extracted by a known volume of food simulant. A typical
migration cell which may be used is the two-sided migration cell described by
Snyder,
R.C., and Breder, C.V., in J. Assoc. Off. Anal. Chem., 68 (4), 770-777, 1985.
Such a
migration cell should incorporate the following features: sample plaques
containing the
cured film having a known surface area and thickness, are separated by inert
spacers,
such as glass beads, so that the simulant flows freely around each plaque; the
headspace should be minimized, and gas-tight and liquid-tight seals should be
maintained, particularly when the migrant is volatile; and the cell should be
subjected to
mild agitation to minimize any localized solubility limitation that might
result in mass-
transfer resistance in the food simulant. Any conventional analytical method
may be
used to determine the quantity of extracted oligomer or residual components
present in
the food simulant. Thus the nature of the extractives may be determined by
suitable
chemical or physical tests, such as NMR, UV-visible spectroscopy, atomic
absorption
spectroscopy, FTIR spectroscopy, mass spectroscopy, gas or liquid
chromatography,
18
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
etc.
In the present invention, the level of extractables is determined using two
methods: organoleptic odor test and analytical instrumental methods. It is
generally
accepted that the residual odor of a cured film can be correlated to residual
unreacted
material in a coating which migrates in the coating and typically is
teachable. This
unreacted material also can be extracted and quantified by analytical
techniques. Odor
is a subjective measurement, but is very important for consumer products where
odors
are objectionable or are indicative of teachable components which can lead to
contamination of foods and drinks and/or to unwanted physiological responses
such as
allergic reactions, dermatitis, etc.
Residual Odor Test
A coating composition is applied over paper board and aluminum foil with #3
Meyer bar then cured, depending on the composition, with UV light (UV curable
compositions) delivering from 120-500 mJ/cm2 of UV energy or cured under
electron
beam conditions of 3 Mrad with165 kV electrons. Coated and cured paper board
and foil
samples of equal dimensions are cut up and placed inside of a 1 liter glass
jar with a
tight "screw on" lid. The jars with samples are placed in oven at 60°C
for 30 min. After
this, several people (at least 5) open each jar and rate odor on a 1 to 5
scale where "1"
is the lowest odor and "5" is the strongest odor. The average score for each
sample is
then reported. Residual odor can be related to amount of unreacted material or
extractables.
Solvent Rub Test
A sample of the cured film is placed on a flat, hard surface with the cured
film
side up. The cured film surface is then repeatedly rubbed to and from with an
applicator
pad saturated with a solvent such as methylethylketone, isopropyl alcohol, or
the like.
The applicator pad typically is a wad of cotton, a soft fabric or a paper
product; and is
applied under normal hand pressure in a to-and-fro rubbing motion. The number
of
times the film surface can be rubbed before deterioration of the film surface
(e.g.,
through dissolution, softening, abrasion, or the like) is a measure of the
solvent
resistance of the cured film. Typically, a cured film is considered solvent
resistant if the
film can be rubbed 10 or more times with the selected solvent, before any
deterioration
is observed and preferably 20 to 75 or more times.
19
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Direct Solvent Extraction
One hundred square centimeters of each cured film is cut into small squares
and
placed into a 16 ml vial. Ten milliliters of solvent (acetonitrile or
methylene chloride) is
added and the sample allowed to stand for 24 hours at room temperature. After
24
hours, 3 ml of the solution is removed, filtered through a 0.2 ~m
polytetraflyoroethylene
filter disk, and placed into an auto-sampler vial for analysis. The extracts
are then
analyzed using high pressure liquid chromotography (HPLC). The mobile phase is
50%
water / 50% methanol, pumped isocratically at 0.8 ml/min at ambient
temperature. The
eluent is analyzed using a photodiode array detector (PDA) monitoring at
205nm. The
column is a Phenomenex~ LUNA Ci$ column, 4.6 mm X 250 mm 5 ~ particle size
with
a high pressure limit of 3400 psi.
Back-Side Extraction With Food Simulant
The food simulant used (extraction solution) is a water/ethanol solution
containing (by volume) 95% ethanol and 5% water. The protocol simulated herein
states that 10 grams of food be exposed to one square inch of packaging film.
Accordingly, 1 ml of extraction solution is added to a 20 ml vial. The
unprinted side of
the UV cured film is placed over the vial opening and a Teflon0 lined cap is
used to seal
it. The surface area (opening) for three vials is 1.1 square inches and the
weight of
fifteen milliliters (3 vials x 5 ml) of extraction solution is 11 grams. The
inverted vials are
placed into an oven and heated at 40°C for ten days. To increase the
detection limit,
extraction solutions from twelve vials are combined and evaporated to less
than 1 ml
then diluted to volume with acetonitrile. This procedure provided a total
extraction area
of 4.4 square inches. The solution is then analyzed. The concentrated sample
is
analyzed following the same HPLC method described above for the Direct
Extraction
method.
The homogeneous aqueous radiation curable composition of this invention will
now be illustrated by the following examples but is not intended to be limited
thereby.
Example 1
80 parts of an aliphatic epoxy acrylate (Laromer LR8765 from BASF), 19.5 parts
of water, and 0.5 parts of an acrylated silicone (Rad 2500 from Tego) were
mixed
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
together to produce a stable coating. This composition is applied by wound
wire rod to
a thickness of 3-6 microns and cured by EB radiation with 3 megarads (Mrads)
of 165kV
electrons. The resulting coating has a gloss >70 and complete cure as
indicated by the
solvent rub test described supra, i.e., more than 30 methyl ethyl ketone (MEK)
double
rubs.
Example 2
77 parts of an aliphatic epoxy acrylate (Laromer LR8765 from BASF), 19.5 parts
of water, 3 parts of a photoinitiator (Irgacure 2959 from Ciba) (and 0.5 parts
of an
acrylated silicone (Rad 2500 from Tego) were mixed together to produce a
stable
coating. This composition is applied by wound wire rod to a thickness of 3-6
microns
and cured by UV radiation with at least 120 mJ/cm2. The resulting coating has
a gloss
>75 and complete cure as indicated by the solvent rub test described supra,
i.e., more
than 20 MEK double rubs.
2p Example 3
30 parts of a highly ethoxylated trimethylolpropane triacrylate (15 mole EO,
SR9035 from Sartomer) and 47 parts of an aliphatic epoxy acrylate (Laromer
LR8765
from BASF), 19.5 parts of water, and 0.5 parts of an acrylated silicone (Rad
2100 from
Tego) were mixed together to produce a stable coating. This composition is
applied by
wound wire rod to a thickness of 3-6 microns and cured by EB radiation with
165kV and
3Mrads. The resulting coating has a gloss >70 and complete cure as indicated
by the
solvent rub test described supra, i.e., more than 18 MEK double rubs.
Example 4
30 parts of an ethoxylated bisphenol A diacrylate (SR602 from Sartomer), 47
parts of an aliphatic epoxy acrylate (Laromer LR8765 from BASF), 19.5 parts of
water,
3 parts of a photoinitiator (Irgacure 2959 from Ciba) (and 0.5 parts of an
acrylated
silicone (Rad 2500 from Tego) were mixed together to produce a stable coating.
This
composition is applied by wound wire rod to a thickness of 3-6 microns and
cured by UV
radiation with at least 120 mJ/cm2. The resulting coating has a gloss >82 and
complete
cure as indicated by the solvent rub test described supra, i.e., more than 40
MEK
double rubs.
21
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Example 5
70 parts of a glycerol-based polyether acrylate (Laromer 8982 from BASF), 10
parts of an epoxy acrylate (91-275 from Reichhold), 15 parts of water, 3 parts
of a
photoinitiator (Irgacure 2959 from Ciba) (and 2 parts of a silicone (L-7602
from Witco)
were mixed together to produce a stable coating. This composition is applied
by wound
wire rod to a thickness of 3-6 microns and cured by UV radiation with at least
120
mJ/cm2. The resulting coating has a gloss >90 and complete cure as indicated
by the
solvent rub test described supra, i.e., more than 15 MEK double rubs.
Example 6
This example demonstrates a red printing ink formulated according to this
invention. 40 parts of a red colorant aqueous dispersion (Sunsperse RHD6012
from
Sun Chemical Pigments Division), 50 parts of an aliphatic epoxy acrylate
(Laromer
LR8765 from BASF), 5 parts of water, 5parts of a photoinitiator (Irgacure 2959
from
Ciba) were mixed together and applied with a flexo hand proofer (300 lines per
inch
anilox) to a thickness of 1-2 microns and cured by UV radiation with at least
250
mJ/cm2. The resulting ink is completely cured as indicated by the solvent rub
test
described supra, i.e., more than 10 IPA double rubs.
Example 7
This example demonstrates a blue printing ink formulated according to this
invention. 30 parts of pigment blue 15:3 (Phthalocyanine blue from
SunChemical) and
70 parts of a highly ethoxylated trimethylolpropane triacrylate (15 mole EO ,
SR9035
from Sartomer) were ground on a three roll mill to form a concentrated base
with a
grind of 2/0; 20 parts of this base was mixed with 40parts of a polyethylene
glycol
(400) diacrylate (SR 344 from Sartomer), 10 parts of a photoinitiator
(Irgacure 2959
from Ciba), 10 parts of highly ethoxylated trimethylolpropane triacrylate (15
mole EO ,
SR9035 from Sartomer) and 40 parts of water to form a blue ink which was
applied with
a flexo hand proofer (300 lines per inch anilox) to a thickness of 1-2 microns
and cured
by UV radiation with at least 250 mJ/cm2. The resulting ink is completely
cured as
indicated by the solvent rub test described supra, i.e., more than 12 IPA
double rubs.
22
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Example 8
The residual odor of the electron beam cured aqueous composition of Example
1 was compared to an electron beam cured conventional composition (Composition
B)
using the "Residual Odor Test" described above.
Composition B: 30 parts of an ethoxylated trimethoylpropane triacrylate
(Photomer 4149 from Cognis), 30 parts of tripropyleneglycol diacrylate (TRPGDA
from
UCB Radcure), 30 parts epoxy acrylate (Epotuf 91-275 from Reichhold ), 7.5
parts of a
benzoate plasticizer (Benzoflex 9-88 from Velsicol), 1 part of a
polyoxypropylene sterate
(Prolam MR-216 from Lambent Technologies), 2 part of a polydimethylsilicone
(L7602
from Witco) , 1 part of a silicone (DC-57 from Dow Corning) and 0.5 parts of a
wax
compound (Bareco wax compound from Carroll Scientific) are thoroughly mixed
together to get a stable coating composition.
As described above in the "Residual Odor Test" protocol, each coating
composition was applied over a paper board and an aluminum foil by wound wire
rod to
a thickness of 3-6 microns and cured by EB radiation with 3Mrads of 165kV
electrons.
As described in the protocol the odor of the samples were rated and the
results are
disclosed in the following Table:
Table 1
Composition Odor on paper Odor on Aluminum foil
Example 1 1.8 1.3
Conventional 3.4 3.3
(Composition B)
23
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Example 9
The residual odor and total extractables of the electron beam cured aqueous
composition of Example 1 was compared to an electron beam cured conventional
composition (Composition C) using the "Residual Odor Test" protocol and the
Direct
Extraction Protocol described above.
Composition C: 40 parts of an ethoxylated trimethoylpropane triacrylate
(EOTMPTA, Photomer 4149 from Cognis), 26 parts of tripropyleneglycol
diacrylate
(TRPGDA, from UCB Radcure), 25 parts epoxy acrylate (Epotuf 91-275 from
Reichhold ), 6.3 parts of a benzoate plasticizer (Benzoflex 9-88 from
Velsicol), 0.7 part
of a polyoxypropylene sterate (Prolam MR-216 from Lambent Technologies) and 2
part
of a polydimethylsilicone (L7602 from Witco) are thoroughly mixed together to
get a
stable coating composition.
As described above in the "Residual Odor Test" protocol, each coating
composition was applied over an aluminum foil by wound wire rod to a thickness
of 3-6
microns and cured by EB radiation with 3Mrads of 165kV electrons. As described
in the
"Residual Odor Test" protocol the odor of the samples were rated. The residual
extractables in each of the coated and cured compositions was determined as
described in the "Direct Solvent Extraction" protocol in which the solvent is
methylene
chloride. The results of each test are disclosed in the following Table:
Table 2
Composition Total Extractables (ppb) Odor on Board
Example 1 <50 2.1
Conventional 3000 EOTMPTA 3.0
(Composition C) 1800 TPGDA
Residual Odor Test
Examples 1 through 9 above were tested via the Residual Odor Test by five
testers and the results are set forth in Table 3 below:
24
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Table 3
Composition odor valueAvera ge Odor
(1-5) Value
1 1 1 2 1 1 1.2
2 2 3 4 2 2 2.6
3 1 2 2 1 1 1.4
4 2 3 3 4 2 2.8
5 2 2 4 3 2 2.6
8 1 2 2 2 1 1.6
9 2 3 3 3 2 2.6
Example 10
The residual extractables of a UV cured aqueous composition of this invention
(Composition D) was compared to a UV cured conventional composition
(Composition
E) using the "Backside Extraction with Food Simulant" protocol described above
in
which the solvent is methylene chloride.
Composition D: 77 parts of an aliphatic epoxy acrylate (Laromer LR8765 from
BASF), 19.5 parts of water and 3 parts of a photoinitiator (KIP 150 from
Lamberti) were
mixed together to produce a stable coating solution.
Composition E: 30 parts of a trimethoylpropane triacrylate (TMPTA, Photomer
4006 from Cognis), 25 parts of tripropyleneglycol diacrylate (TRPGDA from UCB
Radcure), 24 parts epoxy acrylate (Epotuf 91-275 from Reichhold ), 7.0 parts
benzophenone photoinitiator (from Velsicol), 1.0 parts of a dimethyl-benzyl
ketal
photoinitiator (Irgacure 651 from Ciba), 3.0 parts of triethanolamine (from
ChemCentral),
8.0 parts of an acrylated amine (Laromer 8956 from BASF) and 2 parts of a
silicone
(DC57 from Dow Corning) are thoroughly mixed together to get a stable coating
composition.
Each coating composition was applied to paperboard. By wound wire rod to a
thickness of 3-6 microns and cured by UV radiation with a dose of 150 mJ/cm2.
The
residual extractables in each of the coated and cured compositions was
determined as
described in the "Backside Extraction" protocol. The results for each coating
composition are disclosed in the following Table:
25
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Table 4
Coating Composition Backside Extractables
Example 10 <50 ppb Laromer 8765
< 50ppb KIP 150
Conventional 500 ppb TPGDA
(Composition E) 400 ppb TMPTA
1700 ppb Benzophenone
100 ppb Irgacure 651
Example 11
The residual extractables of EB cured aqueous composition of Example 1 of this
invention was compared to EB cured conventional composition (Composition B)
using
the "Backside Extraction with Food Simulant" protocol described above. Each
coating
composition was applied to polyolefin by a wound wire rod to a thickness of 3-
6 microns
and cured by EB radiation with a dose of 3 Mrads at 165 KeV. The residual
extractables in each of the coated and cured compositions was determined as
described in the "Backside Extraction" protocol. The results for each coating
composition are disclosed in the following Table:
Table 5
Coating Composition Backside Extractables (ppb)
Example 1 <50 ppb Laromer 8765
Conventional 125 TMPTA
(Composition B) 95 TPGDA
Example 12
70 parts polyethylene glycol 200 diacrylate (SR259 from Sartomer), 29.5 parts
of
water and 0.5 part of a silicone (DC57 from Dow) were mixed together to
produce a
stable coating. This composition was applied by wound wire rod to a thickness
of 3-6
microns and cured by EB radiation with 165kV electrons and 3 Mrads. The
resulting
coating had a gloss of 80 and was completely cured as indicated by a solvent
rub test
(>25 MEK double rubs).
26
CA 02550008 2006-06-15
WO 2005/066231 PCT/US2004/042132
Example 13
82 parts of polyethyelene glycol 400 diacrylate (SR344 from Sartomer), 14
parts
of water, 3 parts of a photoinitiator (irgacure 2959 from Ciba) and 1.0 part
of an
acrylated silicone (Ebercyl 350 from UCB Radcure) were mixed together to
produce a
stable coating. This composition was applied by wound wire rod to a thickness
of 3-6
microns and cured by UV radiation with at least 180 mJ/cm2. The resulting
coating had
a gloss of 75 and cured completely as indicated by a solvent rub test (>20 MEK
double
rubs).
Those skilled in the art having the benefit of the teachings of the present
invention as hereinabove set forth, can effect numerous modifications thereto.
These
modifications are to be construed as being encompassed within the scope of the
present invention as set forth in the appended claims.
27
